Some previous South Korean reports of North Korean purges and executions have later proved inaccurate.
Indian Prime Minister Narendra Modi will host Chinese President Xi Jinping this year for an informal summit after meeting several times over the past year to try to defuse tension.
The 1st historic summit in Singapore produced little more than a vaguely worded document committing to 'complete denuclearisation'.
The two sides might be able to agree to a formal end of the Korean War, which the North has long called for as a major step towards normalising ties.
Images from North Korean state media shows citizens cheering the state leader as he waved from the train at the start of what could be a 60-hour journey to the Vietnamese capital.
The train's crossing into China follows days of speculation over Kim's secretive travel plans to Hanoi.
About 10 police officers showed up at a local TV station where they were giving an interview, and told them to stop making media appearances or risk being deported.
The leaders are slated to meet in Hanoi on February 27-28 to follow up on their first meeting last June in Singapore.
It will be the second face-to-face for Kim and Trump after a summit in Singapore in June.
Shinzo Abe is seeking to resolve the deeply emotive issue of Japanese nationals kidnapped by North Korean agents during the Cold War era to train Pyongyang's spies.
Reports and sources suggest that Kim Jong-un will make his way to the Hanoi summit either by train or by car.
Sources say Kim will meet with Vietnamese officials when he arrives in Hanoi.
Trump says his representatives have just left North Korea after a very productive meeting and an agreed upon time and date for the second Summit with Kim Jong Un.
A spokesman for President Moon Jae-in says they expect the planned North-US summit would be a turning point in establishing a permanent peace regimen on the Korean peninsula.
Prime Minister Nguyen Xuan Phuc open to facilitate the next summit of the two leaders.
The United States is organising an international summit in Poland next month to focus on Iran's Middle Eastern influence.
In the intervening hours, those leaders had expressed frustration with May's "nebulous" strategy to get the withdrawal treaty past the House of Commons and insisted yet again that they will not renegotiate the text.
Even the word 'multilateralism' itself has fallen out of favour in a group designed to foster international cooperation.
Trump added that at some point he will invite Kim to the United States.
As part of the understanding reached between the two leaders, no additional tariffs will be imposed after Jan 1.
Japan will host a G20 financial leaders' meeting in Fukuoka in western Japan on June 8-9.
Putin said he explained Moscow's position when the leaders met briefly at a summit dinner.
Pompeo acknowledged that the humanitarian crisis in Yemen is serious, but said Washington and Riyadh were offering aid.
The world's two biggest economies have also increasingly been at odds over security in the Asia-Pacific region.